Escalators have been widely used for a long time and their operation is well known. In general, an escalator consists of a plurality of interconnected stairs or steps which move in a closed loop, conveyor fashion between two floors, in effect, providing a moving staircase for transporting passengers. The drive mechanism typically consists of a chain which is driven by an electric motor. The stairs are suitably connected to the chain which pulls the stairs on tracks extending between the floors. The tracks control the position of the stairs to create the staircase and to permit the remaining stairs that return from a floor to be concealed below the staircase.
One appealing feature of escalators is that at the landings the stairs are perfectly level with the landing, permitting passengers to step on and step off of the moving stairs quite easily. In between the landing positions, the stairs assume the staircase arrangement, permiting the passengers to stand comfortably on horizontal surfaces as they are propelled at a steep incline between the floors.
Some newer arrangements do not use staircases but rather a long ramp containing a conveyor belt surface on which the passengers stand. These ramp systems are not really escalators since there are no stairs. Lacking stairs, the ramp incline of these systems must be less than the incline of the typical escalator so that the passengers may stand comfortably on the belt. A gentle incline takes up more space than a steep incline, and an escalator is therefore more "space effective" than the ramp system.
But, a negative characteristic of the conventional escalator and ramp systems alike is that only about 50% of the passenger carrying surface is actually used or available for transporting passengers at any time. The remaining 50%, that returning from the landing, is concealed beneath the staircase portions. This is not energy efficient: energy is lost which could be recaptured by counterbalancing up and down passenger loads by using the other 50% of the stairs.